Motor vehicles can be already equipped with an intelligent driver assistance system for piloted driving in street traffic. With piloted driving, the driver of the vehicle is allowed temporarily not to have to participate in what is going on in the traffic and in the driving tasks, in particular when accelerating, decelerating and steering are carried out automatically. In an activated, trouble-free driving state called “piloted driving”, the driving task of “steering of the front axle” is therefore carried out by means of a front axle steering control, which controls the front axle steering system automatically with an electric power steering system (EPS system). In the event of a failure of this steering system, the driving task “steering” must be taken over for a defined transitional time period by a redundant system.
A generic motor vehicle for this purpose that is already known (GB 2 448 471 A) is provided with a front axle steering system and with a rear axle steering system. If a failure a failure of the front axle steering system is detected with a failure detection device, the steering of the motor vehicle is taken over by the rear axle steering system. Specifically, a direct coupling of the front axle steering to the rear axle steering by means of a switchable coupling is used for this purpose. As a result, an actuator of the rear axle steering takes over also as an actuating element of the front axle steering.
In addition, a motor vehicle equipped with steerable front wheels and with a steering function on the rear wheels is known is also known (EP 1 529 718 A1), which is provided with a system for building up a counter-yaw moment for stabilization of the motor vehicle based on a wheel-individualized brake pressure, and with a reduction of a side slip angle based on the steering function on the rear wheels. The system operates independently of a fault of the front axle steering.
Furthermore, a vehicle is also known (DE 10 2012 207 548 A1), wherein when this is necessary, there is a possibility to initiate a yaw movement of the vehicle with targeted, wheel-selective brake intervention.
It is therefore well known that in case of a failure of the front axle steering control, the steering task can be taken over by the rear axle steering system. However, experiments have shown that simply adjusting the rear axle steering angle is not sufficient with a faulty front steering system, in particular with vehicles moving fast on the roads, in order to influence to a decisive extent the maneuvering of the vehicle and the direction of the travel. Only the slide slip angle is adjusted and the vehicle essentially continues traveling straight ahead.